The focal nature of atherosclerosis, indicated by preferential development of early atherosclerotic lesions in regions of arterial branching and sharp curvature, suggests that local hemodynamic phenomena may play an important role in atherogenesis. To understand the detailed nature of localized (1-100um) phenomena such as flow separation, helical flow patterns, and other secondary flow features which may be present in these regions, a three-dimensional analysis of the flow is necessary. In the present work, numerical simulations of three-dimensional steady, sinusoidally, and physiologically pulsatile flow in which boundary conditions and aortic geometry are specified from experimental measurements in the aorta are obtained by solving a finite element formulation of the Navier-Stokes equations for a Newtonian fluid. The quantitative and qualitative importance of relevant parameters such as Reynolds number, division of flow rate between the two branches, and Womersley number are investigated.